Most electrical appliances break down because of overheating. Overheating of an appliance or a circuit frequently causes fire or electrical shock. In order to provide a kind of protection, most houseware appliances install a fuse to prevent the overheating of the electrical wires. For the building circuitry, the bi-metal type breaker is the most common device installed in the control panel to prevent the overheating of the electrical wiring.
In the other words, those conventional thermal protectors are substantially the electrical current protection for preventing overheating of the electrical wiring. However, the surroundings around the electrical appliance has nothing for protecting against overheating or over-cold. For example, a pot of a coffee maker may also be overheated if there is no more coffee therein. It will also create danger of fire or breaking down situation. A halogen floor lamp would generate a great amount of heat therearound that has a high risk of burning stuff like the curtain around. Moreover, it is well known that the CPU of a computer generates heat during operation. If the heat accumulates around the CPU to a certain extent, the CPU will be malfunctioned. Also, a heater is an appliance for generating heat. However, the user can only control the heat by setting the power output or the timer control. It is relatively expensive and difficult to control the heater according to the actual temperature around the heater.
In fact, every electrical appliance that generates heat needs a thermal guard to prevent the surrounding being overheated or over-cold. It would be a remarkable matter if there is an inexpensive device that can cut the circuit or switch off the appliance if the surrounding thereof is too hot. It not only can prolong the service life of the appliance, but also can help the user to avoid unreasonable hazard or damages.